Abstract

Sand waves are found in the heads of four of five large submarine canyons that incise the northern continental margin of the Bering Sea. The sand waves occur in a restricted depth zone of about 175-490 m. Those in Navarinsky Canyon, the area surveyed in most detail, are best developed in water depths of 300-375 m; they average 5 m in height and about 650 m in wavelength, with crests oriented subparallel to isobaths and almost perpendicular to the axes of the two main branches of the canyon. We speculate that internal-wave currents are responsible for the sand waves. Currents generated by internal waves are a particularly attractive mechanism for at least three reasons: 1) the energy of the internal waves could be amplified in the head of Navarinsky Canyon, especially in the area of the sand wave field; 2) upslope boundary-layer intensification of internal-wave currents might be sufficient to move the sediment composing the sand waves; and 3) the wavelengths of higher-frequency internal waves closely match the spacing of the sand waves. Although we based our assumptions on present-day conditions, we do not know if the sand waves are active. Consequently, we do not discount the possibility that the sand waves could have originated in the Pleistocene when Navarinsky Canyon headed in a shallow embayment that was receiving large quantities of sediment discharged by glacial meltwater streams. These conditions probably caused strong vertical density gradients in the coastal waters, which would have been more favorable than those today for the propagation of high-frequency internal waves.

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